1. Field of the Invention
This invention relates to laser medical device in general and in particular it relates to medical devices for no-contact perforation of a skin of a patient for obtaining blood samples.
2. Description of the Prior Art
Capillary blood sampling is a process for obtaining blood samples from the sub-dermal capillary beds of patients. The traditional methods for the collection of small quantities of blood from patients utilize mechanical perforation of the skin with sharp devices such as metal lancet or needle. This procedure has many drawbacks, two of which are the possible infection of health-care workers or the public at large with the device used to perforate the skin, and the costly handling and disposal of biologically hazardous waste.
Lasers have been used as an efficient precise tool in a variety of surgical procedures. Among sources of laser radiation, the rare-earth elements such as, for example, YAG (yttrium aluminum garnet) crystal doped with erbium (Er) ions are of interest for medicine.
As an active medium one can use various lasant materials to produce different wavelengths of laser light. These materials include, but are not limited to, rare-earth-doped oxide and fluoride laser crystals and glasses. Such crystals and glasses will be doped with impurities to fix the resultant wavelength of the laser.
In the case of lasers, the systems thereof generally include a light source for generating laser light, and optical components for directing the laser beam to a target. The laser source may produce continuous or pulsed laser energy output. The delivery of laser energy to a target specimen and subsequent vaporization of a portion of the specimen often produces byproducts, such as smoke, carbonized particles and/or splattered particles from the specimen. These byproducts pose a threat to the consistent operation of the laser system in that they may be deposited upon the objective optics of the system, thus damaging or altering the optical components, reducing output power, distorting the pattern of energy distribution within the light or laser beam, or otherwise contributing to the degradation of the system.
Methods and devices adapted for perforation of a skin tissue of a patient by means of a focused laser beam have been known in the prior art. The skin perforation is most effective when the wavelength of laser irradiation and the area of intensive absorption of optical emission by live tissue are matched. It is also important to prevent coagulation of a blood during treatment of live tissue by a laser beam. This can be achieved when yittrium-aluminum-erbium-garnet laser with laser emission wavelength of 2.94 microns and laser impulse duration between 50 and 500 microseconds is utilized by the perforation device. In the prior art perforation occurs when a laser beam is focused on the skin tissue, so that a small patch of skin at the area of focusing of the laser beam is evaporated.
Operation of certain medical devices for no-contact perforation of the skin of a patient while obtaining blood samples often produce significant pain and cause fear and apprehension in patients who anticipated a painful experience. Although modern designs of laser perforation devices attempted to eliminate such pain and apprehension, further reduction of patient discomfort would significantly increase the usefulness of new capillary sampling techniques. In the method and apparatus disclosed by U.S. Pat. No. 5,908,416, an attempt has been made to reduce pain in the course of perforation by providing a laser beam having a special shape. However, this approach increases the complexity of the optical system, leads to losses of the laser beam energy, makes the apparatus more expensive and difficult to manufacture. In this device, the increase in compensation of the laser energy should result in higher laser beam divergence ultimately causing skin burns at the area of perforation.
Thus, it has been a need for a laser perforation device capable of reducing pain and apprehension experienced by patients during the blood sampling procedures. It has been also a need for laser perforation devices which are protected from contamination by the products of skin tissue viporization.